In recent years, many fiber-reinforced composite materials have been developed in which a reinforcing material, such as carbon fibers, glass fibers, or aromatic polyamide fibers are impregnated in filament or fabric form into a matrix, like a synthetic resin.
By correctly selecting the matrix and reinforcing material, the known fiber-reinforced materials have a wide-range of excellent properties that can be utilized based on the desired objective of use with respect to mechanical strength, heat resistance, corrosion resistance, electric properties, and weight reduction. The known fiber-reinforced materials are widely used in such technical fields as aerospace, land transportation, shipping, building, construction, industrial parts, and sporting goods.
There are two common uses of the reinforcing fibers. One common use is where the material is impregnated with the reinforcing filaments to form a matrix; while the other use is by parallel alignment of many filaments wide enough to cover the width of the matrix. In the latter use, it is desirable to make the contact area between the matrix and reinforcing filaments as large as possible. Therefore, many reinforcing filaments that are treated with an adhesive (sizing agent) are bundled while having either a flat or ellipsoidal cross-section to form the bundled fibers, in which each reinforcing filament is aligned so as to minimize the space between them, wherein a thin but wide carded sheet is obtained. Impregnation of the carded sheet in the matrix promotes the matrix being impregnated into small spaces, wherein the contact area between the matrix and the reinforcing filament is maximized, and the reinforcing filaments help maximize the reinforcing effects of the fibers.
Accordingly, an airflow carding machine for bundled fibers is disclosed in Japanese Patent Publication No. 3,064,019, wherein a so called suction wind tunnel pipe with a predetermined width is positioned to face a moving path of bundled fibers provided by a supply unit (feed roll) to a take-up section (rewind roll), and wherein the bundled fibers (for example, multifilament) are continuously suctioned in a certain overfed condition to bend the bundled fibers into a crescent shape so the fibers can be carded in the widthwise direction.
The airflow carding machine for the bundled fibers disclosed in Japanese Patent Publication No. 3,064,019 can effectively card the bundled fibers of very long multifilaments in parallel without causing damage.
As shown in FIG. 17, the bundled fibers 1 are drawn from a feed roll A, and then travel through a front feeder 2, which includes a drive roll 2a and a free revolving roll 2b, into which an airflow carding unit 3 cards the fibers 1 to yield a carded sheet 1a. The carded sheet 1a is fed through a back feeder 4 to rewind the sheet 1a around a rewind roll B, wherein the degree of bending of the bundled fiber 1 traveling through a suction wind tunnel 3a of the airflow carding unit 3 is detected by a fiber height detection unit 5.
The fiber height detection unit 5 controls the level of bending of the bundled fibers 1 by pressing down on all of the bundled fibers 1 with a wire-like fiber height sensor unit 5a, and then detects the location of a retaining unit 5b tied with the fiber height sensor unit 5a by a sensor 5c, which feeds back the detected signal to a driver motor of the driving roll 2a. The number of revolutions and the amount of the bundled fibers 1 drawn out by the drive roll 2a and free revolving roll 2b is adjusted according to the amount of bundled fibers being overted as well as to control the amount of bending occurring to the bundled fibers.
As shown in FIG. 18, more than one airflow carding unit 31, 32, and 33 is aligned to form a multistage section in the moving direction of the bundled fibers since a single airflow carding unit 3 alone cannot sufficiently card the bundled fibers. In this case, as shown in FIG. 18, feed roll units 21, 22, 23, and 4 are installed before and after each airflow carding unit 31, 32, and 33 together with the aforementioned fiber height detection units 51, 52, and 53 at each airflow carding unit 31, 32, and 33, respectively, in order to make the carding process proceed smoothly at each airflow carding unit 31, 32, and 33.